CN110336617B - Light receiving module and light module - Google Patents
Light receiving module and light module Download PDFInfo
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- CN110336617B CN110336617B CN201910711778.6A CN201910711778A CN110336617B CN 110336617 B CN110336617 B CN 110336617B CN 201910711778 A CN201910711778 A CN 201910711778A CN 110336617 B CN110336617 B CN 110336617B
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- 230000003287 optical effect Effects 0.000 claims abstract description 62
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- 239000003990 capacitor Substances 0.000 claims abstract description 59
- 230000005540 biological transmission Effects 0.000 claims abstract description 52
- 230000030279 gene silencing Effects 0.000 claims description 6
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- 239000013307 optical fiber Substances 0.000 description 3
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- 230000009286 beneficial effect Effects 0.000 description 1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/66—Non-coherent receivers, e.g. using direct detection
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/66—Non-coherent receivers, e.g. using direct detection
- H04B10/69—Electrical arrangements in the receiver
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Abstract
The invention discloses an optical receiving module and an optical module, wherein the optical receiving module comprises a photodiode, a transimpedance amplifier, an LA+CDR high-speed chip, a sampling resistor, a first cross coupling capacitor, a second cross coupling capacitor, a third cross coupling capacitor, a fourth cross coupling capacitor, a voltage comparison circuit and a reference voltage generation circuit, a sampling voltage signal converted and output by the sampling resistor is compared with a preset reference voltage signal output by the reference voltage generation circuit through the voltage comparison circuit, a direct current alarm signal is output to external transmission equipment when the sampling voltage signal is smaller than the preset reference voltage signal, the direct current alarm is realized, the output current of the transimpedance amplifier is not changed when the temperature is changed, and the voltage comparison circuit directly outputs the direct current alarm signal without being interfered by the LA+CDR high-speed chip, so that the reliability of the optical receiving module is improved.
Description
Technical Field
The present invention relates to the field of optical modules, and in particular, to an optical receiving module and an optical module.
Background
The SFP optical module is a small hot plug optical module conforming to the MSA protocol, provides a bidirectional data transmission function in an optical communication system, and has the characteristics of high transmission rate, small volume and the like.
When the optical receiver in the optical module receives the optical signal, the received optical signal needs to be converted into an electrical signal, the magnitude of the electrical signal is detected and judged, and the alarm and corresponding processing are needed when the electrical signal is too small.
At present, in the process of receiving an alarm by an optical module, a mode of receiving the alarm by a chip manufacturer of the optical module for the optical module is mainly optical modulation amplitude alarm (OMA LOS), namely, the amplitude of modulation amplitude of an electric signal input into the chip is detected in the chip, and then compared with a set reference threshold amplitude, if the amplitude is larger than the threshold amplitude, the alarm is released; if less than the threshold amplitude, an alarm occurs. As shown in fig. 1, fig. 1 is a circuit schematic diagram of a receiving circuit of a conventional light receiving module, which includes a transimpedance amplifier TIA, la+cdr high-speed chips, wherein the transimpedance amplifier and the la+cdr high-speed chips are connected by using cross-coupling capacitors C3 and C4, and output ends of the la+cdr high-speed chips are output by using C1 and C2 cross-coupling. In the light modulation amplitude alarm, the LA+CDR high-speed chip directly detects the TIA output level and carries out amplitude judgment to determine the level state output to the LOS port.
The method has the defects that the electric signal input into the chip is generated by the transimpedance amplifier at the front end, but the transimpedance amplification factor of the transimpedance amplifier is easily influenced by the ambient temperature, the amplification factor is changed, the amplitude of the electric signal input into the rear end chip is changed at the same time, the alarm state of the rear end chip is also changed, and if the amplification factor of the transimpedance amplifier is increased, the alarm value and the alarm removing value of the optical signal are reduced; in contrast, in the low-temperature or high-temperature test, the difference of the alarm values at the two temperatures is 3-5 dB.
The early optical module has low speed and large margin of performance index, so the difference between alarms at low temperature and high temperature does not affect the index. In the later stage, the speed of the optical module is increased, so that the single channel 25G is reached at present, and the current requirement cannot be met by adopting optical modulation amplitude warning.
Disclosure of Invention
The main object of the present invention is to provide a light receiving module, which aims to improve the reliability of the light receiving module.
In order to achieve the above objective, the light receiving module provided by the present invention includes a photodiode, a transimpedance amplifier, a la+cdr high-speed chip, a sampling resistor, a first cross-coupling capacitor, a second cross-coupling capacitor, a third cross-coupling capacitor, a fourth cross-coupling capacitor, a voltage comparison circuit, and a reference voltage generation circuit;
The signal output end of the photodiode is connected with the signal input end of the transimpedance amplifier, the first signal output end of the transimpedance amplifier is connected with the first signal input end of the LA+CDR high-speed chip through the first cross coupling capacitor, the second signal output end of the transimpedance amplifier is connected with the second signal input end of the LA+CDR high-speed chip through the second cross coupling capacitor, the third signal output end of the transimpedance amplifier, the first end of the sampling resistor and the first signal input end of the voltage comparison circuit are interconnected, the second end of the sampling resistor is grounded, the second signal input end of the voltage comparison circuit is connected with the signal input end of the reference voltage generation circuit, the signal output end of the voltage comparison circuit is connected with the first signal input end of the external transmission device, the first signal output end of the LA+CDR high-speed chip is connected with the second signal input end of the external transmission device through the third cross coupling capacitor, and the second signal output end of the LA+CDR high-speed chip is connected with the third signal input end of the external transmission device through the fourth cross coupling capacitor;
The photodiode is used for converting the optical signal received by the optical receiving module into an electrical signal and outputting the electrical signal to the transimpedance amplifier;
the transimpedance amplifier is used for amplifying and converting the electric signal into a differential analog current signal and a sampling current signal, outputting the differential analog current signal to the LA+CDR high-speed chip through the first cross-coupling capacitor and the second cross-coupling capacitor, and outputting the sampling current signal to the sampling resistor;
The la+cdr high-speed chip is configured to perform signal amplitude limiting processing on the differential analog current signal, and output a constant-amplitude digital current signal to an external transmission device through the third cross coupling capacitor and the fourth cross coupling capacitor;
The reference voltage generating circuit is used for outputting a preset reference voltage signal to the voltage comparing circuit;
the sampling resistor is used for converting the sampling current signal into a sampling voltage signal;
the voltage comparison circuit is used for comparing the sampling voltage signal with the preset reference voltage signal and outputting a direct current alarm signal to external transmission equipment when the sampling voltage signal is smaller than the preset reference voltage signal.
Preferably, the voltage comparison circuit comprises a comparator, wherein a non-inverting input end of the comparator is connected with the first end of the sampling resistor, an inverting input end of the comparator is connected with a signal end of the reference voltage generation circuit, and an output end of the comparator is connected with a first signal input end of the external transmission device.
Preferably, the voltage comparison circuit further comprises a positive feedback circuit controlled by closed loop feedback, and the positive feedback circuit comprises a third resistor, a fourth resistor and a fifth resistor;
The first end of the third resistor is connected with the non-inverting input end of the comparator, the second end of the third resistor, the first end of the fourth resistor and the first end of the fifth resistor are connected with each other, the second end of the fourth resistor is grounded, and the second end of the fifth resistor is connected with the output end of the comparator.
Preferably, the voltage comparison circuit further comprises a current limiting resistor, a first end of the current limiting resistor is connected with the first end of the sampling resistor, and a second end of the current limiting resistor is connected with the non-inverting input end of the comparator.
Preferably, the light receiving module further comprises a silence control circuit, wherein a signal input end of the silence control circuit is connected with a signal output end of the voltage comparison circuit, a first signal output end of the silence control circuit is connected with a first signal output end of the la+cdr high-speed chip, and a second signal output end of the silence control circuit is connected with a second signal output end of the la+cdr high-speed chip;
the silence control circuit is used for receiving the direct current warning signal and correspondingly outputting a high-level signal to a first signal output end and a second signal output end of the LA+CDR high-speed chip so as to perform silence control on the LA+CDR high-speed chip.
Preferably, the silence control circuit comprises a first switch, a second switch and a first working voltage input terminal;
the input end of the first switch, the input end of the second switch and the first working voltage input end are interconnected, the output end of the first switch is connected with the first signal output end of the LA+CDR high-speed chip, the output end of the second switch is connected with the second signal output end of the LA+CDR high-speed chip, and the controlled end of the first switch, the controlled end of the second switch and the signal output end of the voltage comparison circuit are interconnected;
The first switch and the second switch are conducted when the voltage comparison circuit outputs a direct current warning signal, and the voltage signal of the first working voltage input end is output to the first signal output end and the second signal output end of the LA+CDR high-speed chip so as to carry out silence control on the LA+CDR high-speed chip.
Preferably, the silence control circuit further comprises a first inductance and a second inductance for isolating high frequency signals;
the first end of the first inductor is connected with the output end of the first switch, and the second end of the first inductor is connected with the first signal output end of the LA+CDR high-speed chip;
The first end of the second inductor is connected with the output end of the second switch, and the second end of the second inductor is connected with the second signal output end of the LA+CDR high-speed chip.
Preferably, the voltage comparison circuit is an MCU with a built-in comparator, a first input end of the MCU is connected with a first end of the sampling resistor, a second input end of the MCU is connected with a signal end of the reference voltage generation circuit, and an output end of the MCU is connected with a first signal input end of the external transmission device;
The MCU is used for inputting the sampling voltage signal and the preset reference voltage signal into the built-in comparator for voltage comparison, and outputting a direct current alarm signal to external transmission equipment when the sampling voltage signal is smaller than the preset reference voltage signal.
Preferably, the MCU is also connected with the LA+CDR high-speed chip;
And the MCU is further used for outputting a silencing control signal to the LA+CDR high-speed chip when the sampling voltage signal is smaller than the preset reference voltage signal so as to perform silencing control on the LA+CDR high-speed chip.
Preferably, the light receiving module further comprises an inverter for performing inversion switching on the direct current warning signal output by the voltage comparison circuit, a signal input end of the inverter is connected with a signal output end of the voltage comparison circuit, and a signal output end of the level inverter is connected with a first signal input end of the external transmission device.
The invention also proposes an optical module comprising an optical transmitting module and an optical receiving module as described above.
According to the technical scheme, a light receiving module is formed by adopting a photodiode, a transimpedance amplifier, a LA+CDR high-speed chip, a sampling resistor, a first cross coupling capacitor, a second cross coupling capacitor, a third cross coupling capacitor, a fourth cross coupling capacitor, a voltage comparison circuit and a reference voltage generation circuit, when the light receiving module receives a light signal, the photodiode converts the light signal received by the light receiving module into an electric signal, the transimpedance amplifier amplifies and converts the electric signal into a differential analog current signal and a sampling current signal, and outputs the differential analog current signal to the LA+CDR high-speed chip through the first cross coupling capacitor and the second cross coupling capacitor, and outputs the sampling current signal to the voltage comparison circuit; the LA+CDR high-speed chip carries out signal amplitude limiting processing on the differential analog current signal, and outputs a digital current signal with equal amplitude to external transmission equipment through a third cross coupling capacitor and a fourth cross coupling capacitor to finish photoelectric signal transmission, meanwhile, the reference voltage generation circuit outputs a preset reference voltage signal to the voltage comparison circuit, the sampling resistor converts the sampling current signal into a sampling voltage signal, the voltage comparison circuit compares the sampling voltage signal converted and output by the sampling resistor with the preset reference voltage signal output by the reference voltage generation circuit, and outputs a direct current alarm signal to the external transmission equipment when the sampling voltage signal is smaller than the preset reference voltage signal, so that the direct current mode alarm is realized, the transimpedance amplifier does not change the output current when the temperature changes, and the voltage comparison circuit directly outputs the direct current alarm signal without being interfered by the LA+CDR high-speed chip, thereby improving the reliability of the light receiving module.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a circuit schematic diagram of a receiving circuit of a conventional light receiving module;
FIG. 2 is a schematic block diagram of a light receiving module according to an embodiment of the invention;
Fig. 3 is a circuit schematic diagram of a light receiving module according to a first embodiment of the present invention;
fig. 4 is a circuit schematic diagram of a light receiving module according to a second embodiment of the present invention;
fig. 5 is a circuit schematic diagram of a light receiving module according to a third embodiment of the present invention;
FIG. 6 is a schematic block diagram illustrating a light receiving module according to another embodiment of the present invention;
fig. 7 is a circuit schematic diagram of a light receiving module according to a fourth embodiment of the present invention;
fig. 8 is a circuit schematic diagram of a light receiving module according to a fifth embodiment of the present invention;
fig. 9 is a circuit schematic diagram of a light receiving module according to a sixth embodiment of the present invention;
fig. 10 is a circuit schematic diagram of a light receiving module according to a seventh embodiment of the invention.
The achievement of the objects, functional features and advantages of the present invention will be further described with reference to the accompanying drawings, in conjunction with the embodiments.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that the description of "first", "second", etc. in this disclosure is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implying an indication of the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and/or" appearing throughout the text is: the system comprises three parallel schemes, wherein an A/B scheme is taken as an example, the scheme comprises an A scheme or a B scheme or a scheme which is simultaneously met by the A and the B, and in addition, the technical schemes among the embodiments can be combined with each other, but the technical schemes are required to be based on the realization that the technical schemes can be realized by a person with ordinary skill in the art, and when the technical schemes are mutually contradictory or can not be realized, the combination of the technical schemes is not considered to exist and is not within the protection scope of the invention.
The invention provides a light receiving module.
Referring to fig. 2, fig. 2 is a schematic diagram of an embodiment of a light receiving module according to the present invention, in the embodiment, the light receiving module includes a photodiode 10, a transimpedance amplifier TIA, a la+cdr high-speed chip U1, a sampling resistor R1, a first cross-coupling capacitor C1, a second cross-coupling capacitor C2, a third cross-coupling capacitor C3, a fourth cross-coupling capacitor C4, a voltage comparison circuit 30, and a reference voltage generation circuit 20;
The signal output end of the photodiode 10 is connected with the signal input end of a transimpedance amplifier TIA, the first signal output end of the transimpedance amplifier TIA is connected with the first signal input end of an LA+CDR high-speed chip U1 through a first cross-coupling capacitor C1, the second signal output end of the transimpedance amplifier TIA is connected with the second signal input end of the LA+CDR high-speed chip U1 through a second cross-coupling capacitor C2, the third signal output end of the transimpedance amplifier TIA, the first end of a sampling resistor R1 and the first signal input end of a voltage comparison circuit 30 are connected, the second signal input end of the sampling resistor R1 is grounded, the second signal input end of the voltage comparison circuit 30 is connected with the signal input end of a reference voltage generation circuit 20, the first signal output end of the LA+CDR high-speed chip U1 is connected with the second signal input end of an external transmission device through a third cross-coupling capacitor C3, and the second signal output end of the LA+CDR high-speed chip U1 is connected with the third signal input end of the external transmission device through a fourth cross-coupling capacitor C4;
A photodiode 10 for converting an optical signal received by the optical receiving module into an electrical signal and outputting the electrical signal to a transimpedance amplifier TIA;
The transimpedance amplifier TIA is used for amplifying and converting an electric signal into a differential analog current signal and a sampling current signal, outputting the differential analog current signal to the LA+CDR high-speed chip U1 through the first cross-coupling capacitor C1 and the second cross-coupling capacitor C2, and outputting the sampling current signal to the sampling resistor R1;
the LA+CDR high-speed chip U1 is used for carrying out signal amplitude limiting processing on the differential analog current signals and outputting constant-amplitude digital current signals to external transmission equipment through a third cross coupling capacitor C3 and a fourth cross coupling capacitor C4;
a reference voltage generating circuit 20 for outputting a preset reference voltage signal to the voltage comparing circuit 30;
the sampling resistor R1 is used for converting a sampling current signal into a sampling voltage signal;
The voltage comparing circuit 30 is configured to compare the sampled voltage signal with a preset reference voltage signal, and output a dc warning signal to an external transmission device when the sampled voltage signal is smaller than the preset reference voltage signal.
In this embodiment, the photodiode 10 of the optical receiving module is configured to receive an optical signal and convert the optical signal into an electrical signal, and because the electrical signal converted by the photodiode 10 is very small and has a uA level, the transimpedance amplifier TIA is required to amplify and convert the electrical signal, the transimpedance amplifier TIA outputs an amplified current signal to the la+cdr high-speed chip U1 through the first cross-coupling capacitor C1 and the second cross-coupling capacitor C2, the la+cdr high-speed chip U1 receives a differential analog current signal, the la+cdr high-speed chip U1 is internally integrated with the limiting amplifier and the clock data recovery chip, and because the electrical signal output by the transimpedance amplifier TIA is an analog current signal, the la+cdr high-speed chip U1 is required to convert the electrical signal into a digital current signal with a constant amplitude, so that an external transmission device recognizes and receives the current signal.
Meanwhile, the current signal output by the transimpedance amplifier TIA is also output to the sampling resistor R1 and converted into a sampling voltage signal, the voltage comparison circuit 30 compares the sampling voltage signal with a preset reference voltage signal, when the sampling voltage signal is greater than or equal to the preset reference voltage signal, the current light signal received by the light receiving module is indicated to be normal, the external transmission device can normally receive and work, when the sampling voltage signal is smaller than the preset reference voltage signal, the current light signal received by the current light receiving module is indicated to be too small to meet the current working requirement, at the moment, the voltage comparison circuit 30 outputs a direct current alarm signal to the external transmission device to realize alarm prompt, at the moment, the light receiving module indirectly detects the light signal through the voltage comparison circuit 30 and directly detects the magnitude of the converted current signal, the detection error problem caused by temperature change of the transimpedance amplifier TIA is avoided, and the detection error problem caused by the temperature change is convenient and reliable.
In this embodiment, the voltage comparison circuit 30 may adopt a hardware circuit such as a comparator U2 or a voltage comparison chip, and may specifically be selected according to requirements, where an output end of the voltage comparison circuit 30 is connected to a first signal input end of an external transmission device, when a sampled voltage signal is greater than a preset reference voltage signal, the voltage comparison circuit 30 outputs a high level to the external transmission device, the external transmission device may determine that a current optical signal is normal according to the high level, and when the sampled voltage signal is less than the preset reference voltage signal, the voltage comparison circuit 30 outputs a low level to the external transmission device, that is, outputs a direct current alarm signal to the external transmission device, and the external transmission device stops working, or outputs a control signal to the optical receiving module to control the optical receiving module to stop working until the optical signal is recovered to be normal.
The reference voltage generating circuit 20 can be a signal generator, a control chip or be composed of a voltage dividing resistor and a voltage source, the reference voltage generating circuit 20 can be regulated and controlled through a port so as to change the output size of a preset reference voltage signal, and the reference voltage generating circuit can be correspondingly arranged according to different customer requirements, so that the purpose of stepless modulation is realized, the compatibility and the reliability of the light receiving module are improved, and the design cost is reduced.
The external transmission equipment can be an optical transceiver, an optical fiber transceiver, a switch, an optical network card, an optical fiber router, an optical fiber high-speed dome camera, a base station, a repeater and the like.
Further, the light receiving module further includes a main control chip (not shown), the signal end of the main control chip is connected with the voltage comparing circuit 30 and the signal output end and the first end of the sampling resistor R1, the main control chip can obtain the current signal output by the transimpedance amplifier TIA through the sampling resistor R1 so as to monitor the light signal of the light receiving module, and meanwhile, can obtain the direct current alarm signal and count, store and forward the direct current alarm signal so as to determine the change condition of the light signal in a preset time period, and feed back the change condition to the external transmission equipment, thereby improving the reliability of the light receiving module.
According to the technical scheme, a light receiving module is formed by adopting a photodiode 10, a transimpedance amplifier TIA, an LA+CDR high-speed chip U1, a sampling resistor R1, a first cross-coupling capacitor C1, a second cross-coupling capacitor C2, a third cross-coupling capacitor C3, a fourth cross-coupling capacitor C4, a voltage comparison circuit 30 and a reference voltage generation circuit 20, when the light receiving module receives a light signal, the light receiving module 10 converts the light signal received by the light receiving module into an electric signal, the transimpedance amplifier TIA amplifies and converts the electric signal into a differential analog current signal and a sampling current signal, and outputs the differential analog current signal to the LA+CDR high-speed chip U1 through the first cross-coupling capacitor C1 and the second cross-coupling capacitor C2, and outputs the sampling current signal to the voltage comparison circuit 30; the LA+CDR high-speed chip U1 carries out signal limiting processing on the differential analog current signal, and outputs a digital current signal with equal amplitude to external transmission equipment through a third cross coupling capacitor C3 and a fourth cross coupling capacitor C4 to finish photoelectric signal transmission, meanwhile, the reference voltage generating circuit 20 outputs a preset reference voltage signal to the voltage comparing circuit 30, the sampling resistor R1 converts the sampling current signal into a sampling voltage signal, the voltage comparing circuit 30 compares the sampling voltage signal converted and output by the sampling resistor R1 with the preset reference voltage signal output by the reference voltage generating circuit 20, and outputs a direct current alarm signal to external transmission equipment when the sampling voltage signal is smaller than the preset reference voltage signal, so that the direct current mode alarm is realized, the transimpedance amplifier TIA can not change the output current when the temperature changes, and the voltage comparing circuit 30 directly outputs the direct current alarm signal without being interfered by the LA+CDR high-speed chip U1, thereby improving the reliability of the light receiving module.
As shown in fig. 3, in an embodiment, the voltage comparing circuit 30 includes a comparator U2, a positive input end of the comparator U2 is connected to a first end of the sampling resistor R1, an negative input end of the comparator U2 is connected to a signal end of the reference voltage generating circuit 20, an output end of the comparator U2 is connected to a first signal input end of the external transmission device, when the sampling voltage signal is greater than a preset reference voltage signal, the comparator U2 outputs a high level to the external transmission device, the external transmission device can determine that the current optical signal is normal according to the high level, when the sampling voltage signal is less than the preset reference voltage signal, the comparator U2 outputs a low level to the external transmission device, that is, outputs a direct current alarm signal to the external transmission device, and the external transmission device stops working, or outputs a control signal to the optical receiving module to control the optical receiving module to stop working until the optical signal is recovered to be normal.
As shown in fig. 4, based on the above embodiment, the voltage comparison circuit 30 further includes a positive feedback circuit 31 of closed-loop feedback control, the positive feedback circuit 31 including a third resistor R3, a fourth resistor R4, and a fifth resistor R5;
The first end of the third resistor R3 is connected with the non-inverting input end of the comparator U2, the second end of the third resistor R3, the first end of the fourth resistor R4 and the first end of the fifth resistor R5 are connected with each other, the second end of the fourth resistor R4 is grounded, and the second end of the fifth resistor R5 is connected with the output end of the comparator U2.
In this embodiment, the comparator U2 and the positive feedback circuit 31 can realize that the comparator U2 has a higher inversion level when the sampling voltage signal changes from low to high, and has a lower inversion level when the sampling voltage signal changes from high to low, and by adding the positive feedback circuit 31, the sampling voltage signal does not oscillate near the critical point of comparison when the sampling voltage signal changes slowly, thereby improving the detection accuracy.
As shown in fig. 5, based on the above embodiment, the voltage comparison circuit 30 further includes a current limiting resistor R2, where a first end of the current limiting resistor R2 is connected to a first end of the sampling resistor R1, a second end of the current limiting resistor R2 is connected to a non-inverting input end of the comparator U2, and the current limiting resistor R2 is used for performing current limiting and voltage division on the sampled voltage signal, so as to avoid an excessive voltage signal at a first signal end of the comparator U2, and improve detection safety.
Specifically, the working principle of the direct current alarm of the light receiving module in this embodiment is as follows:
When the power of the input optical signal is reduced to a certain value, namely the voltage on the sampling resistor R1 is reduced, the comparator U2 is finally caused to output low voltage, namely an alarm is generated; when the input optical signal power rises to a certain value, namely the voltage on the sampling resistor R1 rises, the comparator U2 outputs a high level, namely the alarm is generated.
Setting the voltage of a positive input end of a comparator U2 as Va, the voltage of a negative input end as Vref, the output voltage of the comparator U2 as Vout, the voltage dividing point voltage of a fourth resistor R4 and a third resistor R3 as Vb, the voltage of a sampling resistor R1 as Vr1 and the output photocurrent of TIA as I;
when the output voltage of the comparator U2 is at a low level, i.e. in an alarm state, when the input optical signal increases, I increases with it, and when the positive terminal voltage of the comparator U2 is greater than the sum of the negative terminal voltage and the self-hysteresis voltage Δv of the comparator U2, the output level of the comparator U2 is turned high, i.e. indicated as alarm, according to the above-mentioned available:
Va＝Vref+ΔV
The product can be obtained by the method,
It is finally possible to obtain the product,
The current value is the current value for alarm removal and is recorded as Ia.
When the output voltage of the comparator U2 is at a high level, namely in a warning-removing state, when the input optical signal is reduced, I is reduced along with the reduction, and when the positive terminal voltage of the comparator U2 is smaller than the sum of the negative terminal voltage and the self-hysteresis voltage DeltaV of the comparator U2, the output level of the comparator U2 is turned to be low, namely the warning is indicated.
Va＝Vref-ΔV
The product can be obtained by the method,
Is available in the form of
The current value is the alarming current value and is marked as Ib.
The current difference Ia-Ib of the alarm hysteresis is:
From the above formulas of Ia, ib and Ia-Ib, it can be seen that the alarm and alarm values can be adjusted by modifying the voltage value of the preset reference voltage signal;
The predetermined reference voltage signal does not affect the difference between Ia-Ib, which is constant because Δv is fixed for the comparator U2 and the output voltage Vout is constant for a comparator U2 at constant operating voltage. In the light receiving module, the photoelectric conversion efficiency of the photoelectric converter is relatively stable, so that in the circuit, only the Vref value needs to be adjusted, and the Ia-Ib difference value is unchanged, so that the setting result of the direct current alarm of the light receiving module tends to be stable.
As shown in fig. 6, in order to further improve the reliability of the light receiving module based on the above embodiment, the light receiving module further includes a silence control circuit 40, a signal input terminal of the silence control circuit 40 is connected to a signal output terminal of the voltage comparison circuit 30, a first signal output terminal of the silence control circuit 40 is connected to a first signal output terminal of the la+cdr high-speed chip U1, and a second signal output terminal of the silence control circuit 40 is connected to a second signal output terminal of the la+cdr high-speed chip U1;
The silence control circuit 40 is configured to receive the dc alert signal and correspondingly output a high-level signal to the first signal output end and the second signal output end of the la+cdr high-speed chip U1, so as to perform silence control on the la+cdr high-speed chip U1.
In this embodiment, when the current optical signal does not meet the working requirement, the voltage comparison circuit 30 outputs a dc alarm signal, and the dc alarm signal is simultaneously output to the silence control circuit 40 and the external transmission device, and the external transmission device can determine whether the optical signal received by the current optical receiving module is normal according to the dc alarm signal, and meanwhile, the silence control circuit 40 controls the output of the la+cdr high-speed chip U1.
Specifically, the level signal of the output end of the la+cdr high-speed chip U1 is forcedly set by the output level of the comparator U2, and because the characteristic impedance of the signal output by the la+cdr high-speed chip U1 is single-ended 50 ohms, a pull-up resistor of 50 ohms is arranged in the output port, the pull-up resistor is forcedly pulled up by an external circuit, namely the 50 ohms resistor is short-circuited, so that the capacity of outputting swing amplitude is lost, the purpose of outputting direct current level is achieved, and the function of silence of the output end is realized.
Further, as shown in fig. 7, the silence control circuit 40 includes a first switch K1, a second switch K2, and a first operating voltage VCC input terminal;
the input end of the first switch K1, the input end of the second switch K2 and the input end of the first working voltage VCC are interconnected, the output end of the first switch K1 is connected with the first signal output end of the LA+CDR high-speed chip U1, the output end of the second switch K2 is connected with the second signal output end of the LA+CDR high-speed chip U1, and the controlled end of the first switch K1, the controlled end of the second switch K2 and the signal output end of the voltage comparison circuit 30 are interconnected;
The first switch K1 and the second switch K2 are turned on when the voltage comparison circuit 30 outputs the dc alert signal, and output the voltage signal of the first operating voltage VCC input end to the first signal output end and the second signal output end of the la+cdr high-speed chip U1, so as to perform silence control on the la+cdr high-speed chip U1.
In this embodiment, when the voltage comparison circuit 30 outputs the dc alert signal, the first switch K1 and the second switch K2 are turned on, and then the signals of the two output ends of the la+cdr high-speed chip U1 are forced to be pulled up to the first working voltage VCC, the pull-up 50 ohm resistor of the output end is shorted, the la+cdr high-speed chip U1 loses the capability of outputting the swing amplitude, so as to implement the function of silence, and when the alarm is removed, the first switch K1 and the second switch K2 are turned on and off, the capability of recovering the output swing amplitude of the output port is restored, and silence is cancelled.
Since the on or off of the silence is controlled entirely by the compared output levels, the on or off time of the silence is determined by the input-to-output transmission time and the output level transition time of the comparator U2, and in general, the time can reach less than 1 microsecond, even tens of nanoseconds.
As shown in fig. 8, the silence control circuit 40 further includes a first inductance L1 and a second inductance L2 for isolating high frequency signals;
the first end of the first inductor L1 is connected with the output end of the first switch K1, and the second end of the first inductor L1 is connected with the first signal output end of the LA+CDR high-speed chip U1;
the first end of the second inductor L2 is connected with the output end of the second switch K2, and the second end of the second inductor L2 is connected with the second signal output end of the LA+CDR high-speed chip U1.
In this embodiment, the first inductor L1 and the second inductor L2 are used for isolating high-frequency signals, so as to avoid that the output end of the la+cdr high-speed chip U1 cannot realize the silence function due to the input of external high-frequency signals to the la+cdr high-speed chip U1.
In an embodiment, the first switch K1 and the second switch K2 are level control switches, such as transistors or field effect transistors, for example, when the first switch K1 and the second switch K2 are turned on at a high level and turned off at a low level, the first switch K1 and the second switch K2 may be level control switches such as NPN transistors or NMOS transistors, etc., when the first switch K1 and the second switch K2 are turned on at a low level and turned off at a high level, the first switch K1 and the second switch K2 may be level control switches such as PNP transistors and PMOS transistors, etc., and specific types of the first switch K1 and the second switch K2 may be correspondingly set according to the turn-on mode of the silence control circuit 40, which is not limited herein.
In another embodiment, as shown in fig. 9, the voltage comparison circuit 30 is an MCU with a built-in comparator, a first input end of the MCU is connected to a first end of the sampling resistor R1, a second input end of the MCU is connected to a signal end of the reference voltage generation circuit 20, and an output end of the MCU is connected to a first signal input end of the external transmission device;
And the MCU is used for inputting the sampling voltage signal and the preset reference voltage signal into the built-in comparator for comparison and outputting a direct current alarm signal to external transmission equipment when the sampling voltage signal is smaller than the preset reference voltage signal.
In this embodiment, the reference voltage generating circuit includes a reference voltage input end, a sixth resistor R6 and a seventh resistor R7, the reference voltage is divided by the sixth resistor R6 and the seventh resistor R7 and then outputs a preset reference voltage to the MCU, as shown in fig. 10, the photocurrent output by the transimpedance amplifier TIA is converted into a voltage signal by the sampling resistor R1 and is output to the inverting input end of the built-in comparator of the MCU, the non-inverting input end of the comparator is obtained by dividing the reference voltage Vref by the sixth resistor R6 and the seventh resistor R7, a voltage is set for the preset reference voltage signal, that is, the alarm threshold, and the output voltage of the built-in comparator is directly output outwards, wherein the sixth resistor R6 pulls up the reference voltage Vref, and the voltage is not influenced by the pulling bias of the external VCC, so that the stable state is maintained. When the received light power input to the light receiving module is reduced, the current output by the transimpedance amplifier TIA is reduced, the voltage generated on the sampling resistor R1 is reduced to be smaller than the sum of the voltage division value of the sixth resistor R6 and the seventh resistor R7, the MCU outputs a high level, the light receiving module alarms at the moment, wherein a hysteresis interval of a positive phase input end and a negative phase input end can be set in the built-in comparator and used as hysteresis of an alarm and an alarm, so that a more accurate reference voltage value can be set, the alarm can be more accurate, when the received light power input to the light receiving module is increased, the photocurrent output by the transimpedance amplifier TIA is increased, the voltage on the sampling resistor R1 is increased to be larger than the sum of the voltage division value of the sixth resistor R6 and the seventh resistor R7 and the hysteresis interval value, the MCU outputs a low level, the light receiving module alarms at the moment, the resistance value of the sixth resistor R6 and the seventh resistor R7 can be correspondingly adjusted, and the reference voltage can be correspondingly adjusted, so that different preset reference voltage signals can be adapted to the alarm threshold voltage signals to be provided for the MCU.
It can be understood that the MCU may also perform level conversion on the output signal of the built-in comparator according to the requirement, so the dc alert signal may be a high level signal or a low level signal, which is not limited herein.
As shown in fig. 10, further, the MCU is also connected to the la+cdr high-speed chip U1;
And the MCU is also used for outputting a silencing control signal to the LA+CDR high-speed chip U1 when the sampling voltage signal is smaller than the preset reference voltage signal so as to perform silencing control on the LA+CDR high-speed chip U1.
Specifically, when the MCU outputs the dc alert signal, the MCU further sets the clock data recovery chip CDR in the la+cdr high-speed chip U1 through the IIC port, so as to perform silence control on the la+cdr high-speed chip U1. When 1 is set, the clock data recovery chip CDR output in the LA+CDR high-speed chip U1 is a direct current level, and no swing is output, so that silence control is realized; when the alarm is removed, the MCU can remove the clock data recovery chip CDR in the LA+CDR high-speed chip U1 through the IIC, and when the clock data recovery chip CDR is 0, the output swing of the clock data recovery chip CDR in the LA+CDR high-speed chip U1 is represented, and the silence control is cancelled.
Further, the light receiving module further includes an inverter (not shown) for switching the dc alert signal outputted from the voltage comparing circuit 30 in reverse, a signal input terminal of the inverter is connected to a signal output terminal of the voltage comparing circuit 30, and a signal output terminal of the level inverter is connected to a first signal input terminal of the external transmission device.
In this embodiment, an inverter with a level inversion function is connected in series to the output end of the comparator U2, so that the requirements of different light receiving modules on the alarm level and the alarm level removal can be met, and the compatibility of the light receiving modules is improved.
The invention also provides an optical module, which comprises an optical transmitting module and an optical receiving module, wherein the specific structure of the optical receiving module refers to the embodiment, and the optical module at least has all the beneficial effects brought by the technical schemes of the embodiment because the optical module adopts all the technical schemes of all the embodiments, and the detailed description is omitted.
In this embodiment, the light receiving module and the light emitting module are disposed in the same module to form an integrated light module, and simultaneously have both a light emitting function and a light receiving function, where the light emitting module is used for converting an electrical signal into an optical signal, and the light receiving module is used for converting the optical signal into an electrical signal.
The foregoing description is only of the preferred embodiments of the present invention and is not intended to limit the scope of the invention, and all equivalent structural changes made by the description of the present invention and the accompanying drawings or direct/indirect application in other related technical fields are included in the scope of the invention.
Claims (11)
1. The light receiving module is characterized by comprising a photodiode, a transimpedance amplifier, a LA+CDR high-speed chip, a sampling resistor, a first cross-coupling capacitor, a second cross-coupling capacitor, a third cross-coupling capacitor, a fourth cross-coupling capacitor, a voltage comparison circuit and a reference voltage generation circuit;
The signal output end of the photodiode is connected with the signal input end of the transimpedance amplifier, the first signal output end of the transimpedance amplifier is connected with the first signal input end of the LA+CDR high-speed chip through the first cross coupling capacitor, the second signal output end of the transimpedance amplifier is connected with the second signal input end of the LA+CDR high-speed chip through the second cross coupling capacitor, the third signal output end of the transimpedance amplifier, the first end of the sampling resistor and the first signal input end of the voltage comparison circuit are interconnected, the second end of the sampling resistor is grounded, the second signal input end of the voltage comparison circuit is connected with the signal input end of the reference voltage generation circuit, the signal output end of the voltage comparison circuit is connected with the first signal input end of the external transmission device, the first signal output end of the LA+CDR high-speed chip is connected with the second signal input end of the external transmission device through the third cross coupling capacitor, and the second signal output end of the LA+CDR high-speed chip is connected with the third signal input end of the external transmission device through the fourth cross coupling capacitor;
The photodiode is used for converting the optical signal received by the optical receiving module into an electrical signal and outputting the electrical signal to the transimpedance amplifier;
the transimpedance amplifier is used for amplifying and converting the electric signal into a differential analog current signal and a sampling current signal, outputting the differential analog current signal to the LA+CDR high-speed chip through the first cross-coupling capacitor and the second cross-coupling capacitor, and outputting the sampling current signal to the sampling resistor;
The la+cdr high-speed chip is configured to perform signal amplitude limiting processing on the differential analog current signal, and output a constant-amplitude digital current signal to an external transmission device through the third cross coupling capacitor and the fourth cross coupling capacitor;
The reference voltage generating circuit is used for outputting a preset reference voltage signal to the voltage comparing circuit;
the sampling resistor is used for converting the sampling current signal into a sampling voltage signal;
the voltage comparison circuit is used for comparing the sampling voltage signal with the preset reference voltage signal and outputting a direct current alarm signal to external transmission equipment when the sampling voltage signal is smaller than the preset reference voltage signal.
2. The light receiving module as claimed in claim 1, wherein the voltage comparing circuit includes a comparator, a non-inverting input terminal of the comparator is connected to the first terminal of the sampling resistor, an inverting input terminal of the comparator is connected to the signal terminal of the reference voltage generating circuit, and an output terminal of the comparator is connected to the first signal input terminal of the external transmission device.
3. The light receiving module of claim 2, wherein the voltage comparison circuit further comprises a closed loop feedback controlled positive feedback circuit comprising a third resistor, a fourth resistor, and a fifth resistor;
The first end of the third resistor is connected with the non-inverting input end of the comparator, the second end of the third resistor, the first end of the fourth resistor and the first end of the fifth resistor are connected with each other, the second end of the fourth resistor is grounded, and the second end of the fifth resistor is connected with the output end of the comparator.
4. The light receiving module as recited in claim 3, wherein the voltage comparison circuit further comprises a current limiting resistor, a first end of the current limiting resistor being connected to the first end of the sampling resistor, and a second end of the current limiting resistor being connected to the non-inverting input of the comparator.
5. The light receiving module of claim 4, further comprising a silence control circuit, a signal input of the silence control circuit being connected to a signal output of the voltage comparison circuit, a first signal output of the silence control circuit being connected to a first signal output of the la+cdr high speed chip, a second signal output of the silence control circuit being connected to a second signal output of the la+cdr high speed chip;
the silence control circuit is used for receiving the direct current warning signal and correspondingly outputting a high-level signal to a first signal output end and a second signal output end of the LA+CDR high-speed chip so as to perform silence control on the LA+CDR high-speed chip.
6. The light receiving module of claim 5, wherein the silence control circuit comprises a first switch, a second switch, and a first operating voltage input;
the input end of the first switch, the input end of the second switch and the first working voltage input end are interconnected, the output end of the first switch is connected with the first signal output end of the LA+CDR high-speed chip, the output end of the second switch is connected with the second signal output end of the LA+CDR high-speed chip, and the controlled end of the first switch, the controlled end of the second switch and the signal output end of the voltage comparison circuit are interconnected;
The first switch and the second switch are conducted when the voltage comparison circuit outputs a direct current warning signal, and the voltage signal of the first working voltage input end is output to the first signal output end and the second signal output end of the LA+CDR high-speed chip so as to carry out silence control on the LA+CDR high-speed chip.
7. The light receiving module of claim 6, wherein the silence control circuit further comprises a first inductance and a second inductance for isolating high frequency signals;
the first end of the first inductor is connected with the output end of the first switch, and the second end of the first inductor is connected with the first signal output end of the LA+CDR high-speed chip;
The first end of the second inductor is connected with the output end of the second switch, and the second end of the second inductor is connected with the second signal output end of the LA+CDR high-speed chip.
8. The light receiving module according to claim 1, wherein the voltage comparing circuit is an MCU with a built-in comparator, a first input terminal of the MCU is connected to the first terminal of the sampling resistor, a second input terminal of the MCU is connected to the signal terminal of the reference voltage generating circuit, and an output terminal of the MCU is connected to the first signal input terminal of the external transmission device;
The MCU is used for inputting the sampling voltage signal and the preset reference voltage signal into the built-in comparator for voltage comparison, and outputting a direct current alarm signal to external transmission equipment when the sampling voltage signal is smaller than the preset reference voltage signal.
9. The light-receiving module of claim 8, wherein the MCU is further connected to the la+cdr high-speed chip;
And the MCU is further used for outputting a silencing control signal to the LA+CDR high-speed chip when the sampling voltage signal is smaller than the preset reference voltage signal so as to perform silencing control on the LA+CDR high-speed chip.
10. The light-receiving module according to claim 1, further comprising an inverter for inverting switching of the direct-current warning signal outputted from the voltage comparison circuit, a signal input terminal of the inverter being connected to a signal output terminal of the voltage comparison circuit, a signal output terminal of the inverter being connected to a first signal input terminal of the external transmission device.
11. An optical module comprising an optical transmitting module and an optical receiving module as claimed in any one of claims 1-10.
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| CN113281853B (en) * | 2020-02-19 | 2023-01-20 | 青岛海信宽带多媒体技术有限公司 | Optical module |
| CN111600660B (en) * | 2020-05-13 | 2021-08-31 | 成都优博创通信技术股份有限公司 | Optical communication device, OLT equipment and communication link |
| CN113949448A (en) * | 2020-07-16 | 2022-01-18 | 青岛海信宽带多媒体技术有限公司 | Optical module receiving optical power monitoring method and optical module |
| CN111740785B (en) * | 2020-08-24 | 2020-12-08 | 深圳市迅特通信技术有限公司 | PAM4 optical module receiving and output control circuit, method and system |
| CN112968734B (en) * | 2021-02-24 | 2022-05-03 | 东莞铭普光磁股份有限公司 | Optical module, method for realizing network management function of optical module and optical communication equipment |
| CN117081576B (en) * | 2023-08-29 | 2024-01-26 | 苏州优达光电子有限公司 | High-speed steady-state optocoupler |
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